Heretofore, an image read device that is called a sheet-through type is known which conveys an original in a sub-scanning direction and passes the conveyed original through a fixed read position, thereby performing sub-scanning on images of the original. A transparent member is arranged at the read position of an image read unit in order to pass light emitted by a light source inside the image read unit toward the original on the outside or light reflected by an image surface of the original and projected toward the inside of the image read unit. In this type of image read device, because the original passes in contact with the transparent member when the images of the original are read, it is inevitable that dust, or the like, sticking to the image-surface side of the original adheres to the transparent member. Furthermore, if an adhering material such as dust adheres to the read position of the transparent member, its effect appears on read image signals and the images are deteriorated. The material adhering to the transparent member causes image deterioration in an image read device of not only the sheet-through type but also other types. However, the effect appears on images as only a “point” in a type of image read device in which an original is fixed and an image read unit is moved in the sub-scanning direction to read the images, while it results in what is called a longitudinal line that extends in the sub-scanning direction and significant image deterioration is caused in a sheet-through type image read device.
Patent Document 1(Japanese Patent No: 3832483) describes an original read device that includes a moving unit to move a transparent member back and forth in an original conveying direction and a control unit that conveys the original and moves the transparent member by using the moving unit while causing the images to be read at a read position. Thus, because the transparent member is moved during the operation of reading the original, the reading of the images of the original is always performed at a different position of the transparent member; therefore, even if an adhering material such as dust or dirt is present on the transparent member, the decrease in image quality due to a longitudinal line can be prevented.
Furthermore, if an event causing the interruption of original conveyance occurs such as the occurrence of a jam of the original, the original read device described in Patent Document 1 stops the transparent member and, if an automatic document feeder (hereinafter, referred to as an ADF) that conveys the original to the read position is not opened with respect to a scanner, performs a control to return the transparent member to the home position. Thus, because the transparent member is in the home position upon reading of a subsequent original, it is possible to start reading the original in a smoother manner compared to the one that starts to read the original after returning the transparent member, which is not in the home position, to the home position.
However, in the above-described original read device, when an event causing the interruption of original conveyance occurs, the original being conveyed is stopped in an original conveying path. In the original read device described in Patent Document 1, the transparent member returns to the home position without any reference to the stop position of the original that is stopped in the above-described original conveying path. As a result, there is a possibility that the original will be damaged if the original is stopped in the state described below.
For example, in a device in which the home position is set on the most downstream side in the movable range of a transparent member as illustrated in FIG. 18A, if an original MS is stopped with the rear edge of the original located between the original conveying-direction downstream end of a transparent member 154 and a scoop guide member 156, damage to the original MS occurs as described below. Specifically, if the transparent member 154 is moved in the same direction as the original conveying direction in order to return the transparent member 154 to the home position, the rear edge of the original MS is in contact with the original conveying-direction downstream end of the transparent member 154 and the rear edge of the original MS is moved in the original conveying direction together with the transparent member 154. However, the leading edge of the original MS is sandwiched between discharge roller pair 92 and cannot be moved. Therefore, as illustrated in FIG. 18B, when the transparent member 154 returns to the home position, the part on the original conveying-direction upstream side from the discharge roller pair 92 is forcibly folded up in the conveying path and becomes crumpled, whereby the original is damaged.
Moreover, as illustrated in FIG. 19A, in a configuration where a flexible guide member 251 is arranged which is fixed to the downstream end of the transparent member 154 and is moved along a guide surface of the scoop guide member 156 together with the transparent member 154, the original is damaged if the original MS is stopped in a state where the rear edge of the original is placed on the guide surface of the scoop guide member 156. Specifically, if the transparent member 154 is moved in the same direction as the original conveying direction in order to return the transparent member 154 to the home position, the rear edge of the original MS is in contact with the original conveying-direction downstream end of the flexible guide member 251 and the rear edge of the original MS is moved in the original conveying direction along the guide surface of the scoop guide member 156 together with the flexible guide member 251. However, the leading edge of the original MS is sandwiched between the discharge roller pair 92 and cannot be moved. Therefore, as illustrated in FIG. 19B, when the transparent member 154 returns to the home position, the part of the original on the original conveying-direction upstream side from the discharge roller pair 92 is folded up in the conveying path and becomes crumpled, whereby the original is damaged.
Furthermore, in a device where the home position is set on the most upstream side in the movable range of the transparent member, as illustrated in FIG. 20A, if a jam of the original occurs because the leading edge of the original MS is in contact with an opposing guide member 97 and is bent over toward the transparent member to be in contact with the transparent member 154, damage to the original occurs. Specifically, when the transparent member 154 is moved in the direction opposite to the original conveying direction in order to return the transparent member 154 to the home position, the leading edge of the original MS is moved in the direction opposite to the original conveying direction together with the transparent member 154 and, as illustrated in FIG. 20B, the leading edge of the original is further bent over and jammed between a cover member 157, which contains a part of the transparent member 154, and the transparent member 154. Because the cover member 157 and the transparent member 154 are members on the side of the scanner, if an ADF 51 is opened with respect to a scanner 150, as illustrated in FIG. 20C, in a state where the leading edge of the original MS is jammed in the gap between the transparent member 154 and the cover member 157, the jammed part remains on the side of the scanner 150. On the other hand, because the vicinity of the rear edge of the original MS is sandwiched between the registration roller pair 89, the remaining part of the original MS is moved together with the ADF 51. As a result, the jammed part of the original MS is torn and the original is damaged.
Moreover, as illustrated in FIG. 21A, the original is damaged if the transparent member 154 returns to the home position on the most upstream side in the movable range of the transparent member in a state where the rear edge of the stopped original is located near the cover member 157 on the transparent member. Specifically, when the transparent member 154 is moved in the direction opposite to the original conveying direction in order to return the transparent member 154 to the home position, the original part on the transparent member 154 is moved in the direction opposite to the original conveying direction together with the transparent member 154 and, as illustrated in FIG. 21B, the rear edge of the original MS is jammed in the gap between the cover member 157 and the transparent member 154. Then, as illustrated in FIG. 21C, if the ADF 51 is opened with respect to the scanner 150, the jammed part remains on the scanner side. On the other hand, because the vicinity of the leading edge of the original MS is sandwiched between the discharge roller pair 92, the leading edge part of the original MS is moved together with the ADF 51. As a result, the jammed part of the original is torn and the original is damaged.
The present invention has been made in consideration of the above problems and it is an object of the present invention to provide an image read device and a copier that can perform image reading in a smooth manner after an event causing the interruption of original conveyance is resolved and prevent damage to the original.